1. Field of the Invention
The invention relates to a medical aspirator and, more particularly, to a system that is microprocessor-controlled and methods of control and operation therefor.
2. Description of the Related Art
Suction, or the application of a vacuum to a patient, has many uses within medicine. It is used within the pre-hospital care, home care and hospital environments to help clear a patient's airway, to remove debris from a surgical site, to provide gastrointestinal and wound drainage, and in some cases to help inflate a collapsed lung by providing mild negative pressure in the pleural cavity. Because of diversity within the patient population range (infant through adult) and the variety of procedures that are possible, each procedure has its own permissible vacuum and airflow ranges, and as a result, almost all suction devices are designed for a specific procedural use.
The usage environment has always dictated the types of suction apparatus that are commonly used.
In the pre-hospital care environments the primary use of portable devices is to provide relatively high vacuum and high airflow to the unprotected upper airway and to provide low vacuum and high airflow to the protected airway. The home care environment requires electrically powered devices that have adjustable vacuum (low to high) and high airflow for the removal of airway secretions as part of a patient's pulmonary toilet.
In the hospital environment a wide range of electrically powered suction devices is found. There are units whose performance is designed to provide suction and flow to the upper airway as described above; units that can provide high vacuum and high airflow to remove blood, bone and tissue debris from surgical sites; units that provide a mild vacuum and flow for drainage around wound sites; units that intermittently provide mild vacuum and flow for drainage of the gastrointestinal tract; units for draining the digestive tract; and units that provide low vacuum and high flow levels for pleural cavity evacuation. The required number of each type of suction apparatus is affected by seasonal patient population changes and the patient composition existing within these populations. This seasonal variability is quite common and results in many hospitals having to rent additional devices to augment their inventory.
Previous devices were limited in their ability to perform in more than two of the modes described above because their simple pneumatic controls lacked the ability to meet the flow, pressure and timing requirements inherent in the various operating modes. If an economically viable aspirator were available that met the gamut of clinical requirements, then civilians and military providers would have a single unit that meets their clinical and mission needs. In addition, a need has always existed for a multi-function suction apparatus for military or other remote pre-hospital or hospital applications.
Suction may be generated by pneumatic, manual power or electrical power.
Suction derived from manual power is generated when an operator physically causes a mechanical pump mechanism to be cycled back and forth. Manually powered suction devices produce irregular and difficult to control suction and are used almost exclusively in the emergency environment. Not surprisingly, their use is restricted to emergency suctioning of a patient's upper airway.
Suction derived from pneumatic power is generated when gas, flowing at high velocity past an orifice (venturi), produces a vacuum at the orifice. This occurrence is commonly referred to as the Bernoulli Effect. The amount of vacuum is controlled by increasing or decreasing the flow of gas past this orifice which may negatively impact the desired suction applied to the patient. This method typically uses oxygen as its source of gas power and is rarely used in the emergency and hospital environments anymore due to the large amounts of oxygen they consume. Pneumatically powered suction, when used, is limited mostly to emergency suctioning of a patients upper airway.
Suction derived from electrically powered sources may obtain its operating power from alternating current (AC), or direct current (DC), or from a battery pack or fuel cell. Electrically powered suction devices use a motor driven vacuum pump or thermally-cycled mechanisms to create suction. The characteristics of the pumps will ultimately determine the medical application to which they are applied. Electrically powered suction devices are the most common and are in widespread use throughout the pre-hospital, home care and hospital environments.
Designers have improved medical suction systems by incorporating smaller and/or more powerful pumps, state-of-the-art battery technology for portable variants and battery recharging technology related thereto, and via the use of more sophisticated collection reservoirs (both disposable and reusable) that incorporate mechanical shut-off valves and filters (both bacteriostatic and/or hydrophobic). Control of suction devices has been relegated to simple on/off switches and circuits, and vacuum limiting mechanisms that consist of bleed-type valves that entrain ambient air as a means by which to limit the vacuum applied to the patient. The interface to these devices consists of simple indicators such as illuminating lamps and/or mechanical vacuum gauges—typically of the bourdon-tube type.
In a few instances, designers have produced devices, capable of providing more than one mode of operation. The resultant devices are invariably bigger, heavier, more complex, more prone to malfunction and predicatively more expensive.
A very effective aspirator intended for use in ambulances is shown in U.S. Pat. No. 5,954,704. U.S. Pat. No. 5,954,704 is assigned to the assignee of the subject invention and the disclosure is incorporated herein by reference.